1. Field of the Invention
This invention relates to a fire alarm system and more particularly to a fire alarm system which is capable of computing and preestimating, on the basis of analog data, such as a temperature, a density of CO gas, or a density of smoke detected by a fire detector or detectors, a degree of danger which will threaten the people in the near future, so as to give an alarm preliminarily when the estimated degree of danger is above the predetermined level.
2. Relevant Arts
Recently, an analog intelligent fire alarm system in which a central signal station receives detection data from an analog type detector and makes a fire determination based on the detection data has been researched and developed.
Heretofore, there have been proposed, for example, a system in which the detection data obtained continuously from the analog type detector is compared with a predetermined threshold value to determine a fire and a system in which an amount of a change in the detection data from the analog type detector is computed every predetermined period to make a fire determination when the amount of the change exceeds a predetermined value.
These systems, however, involve such a problem that they are easily influenced by transitory noises.
In addition, it is difficult for the fire alarm systems of this type to grasp a spreading tendency of a fire. For instance, there is a serious problem in case of a flaming fire which develops abrupt temperature rise after a certain period of time from the start of a fire. In this case, sometimes, the fire has spreaded when the central signal station makes a fire determination and the escape from the fire is started only after the fire becomes very dangerous for people.